1. Field
The following description relates to inter-network handover, and more particularly, to an apparatus for controlling handover between heterogeneous networks, a method of performing handover between heterogeneous networks in a mobile router, and a mobile router.
2. Description of the Related Art
A mobile network in a vehicle such as a high-speed train having a mobile router and a fixed node uses mobile network technology based on Internet protocol version 4 (IPv4). When handover occurs between domains in the mobile network, packets transmitted from a correspondent node during visited network movement detection, agent detection, and a registration process are lost. Thus, a high-speed handover procedure is required.
For this reason, a technique of applying fast mobile IPv6 to mobile nodes while a high-speed mobile router moving at speeds in excess of 300 km/h like a high-speed train is performing handover has been suggested. The mobile router moves from an access router before handover, receives prefix information corresponding to a new access router, and then transmits the information to a mobile node. The mobile router and the mobile node request the previous access router for fast IPv6 binding update.
The previous access router and the new access router exchange handover initiate and notification messages according to fast IPv6 binding, and the previous access router transmits a fast binding acknowledgement message to the mobile node. Then, data sent to the mobile router and the mobile node using a previous prefix is transmitted from the previous access router via the new access router through a tunnel. When the mobile router receives the fast binding acknowledgement message, it immediately transmits a zero lifetime message for releasing the previous prefix to the mobile node, and then the mobile node transmits the data using the new prefix.
Fast mobile IPv6 used for handover as described above prevents packet loss during communication between a mobile node and a correspondent node while a mobile router is performing handover, and also reduces handover delay. However, a vehicle such as a high-speed train has small mobile cells, and thus probability of handover failure increases when the vehicle passes through several cells at high speed. Also, minimum time required for handover between cells is not ensured, and thus packets are lost.
Meanwhile, there is another technique for applying handover between satellite and wireless networks to a high-speed mobile router using a link trigger signal of multiple interfaces. According to this technique, a mobile router having multiple interfaces controls handover between mobile networks using sequential link up/down trigger signals. This technique prevents packet loss and session interruption regardless of movement speed of the mobile router, and when handover is performed between a terrestrial wireless home network and a visited satellite network, reduces power consumption by placing an inactivated network access interface in a sleep state. However, when the high-speed train that is providing service in a visible region of the satellite network enters a shadow region of the satellite network, handover to an interoperable wireless network should be immediately performed to continue the service. In this case, the mobile router passes through cells of the wireless network at high speed, and thus it is difficult to detect mobility using a link trigger signal. In other words, handover to the corresponding wireless network may fail, or time taken to perform handover may increase.